This is why those among the practitioners of speculative theology and rational inquiry who went astray did so in matters involving statements of fact: they opposed what Allah declares about Himself and His creation with their own reason and opinions. Those among the practitioners of worship and jurisprudence who went astray did so in prescriptive matters: they opposed Allah’s commands, which constitute His divine law, with their own desires and opinions.

The point here is that opposing the statements of the Messengers with those of others is a practice of the unbelievers, as Allah Most High says:

“None dispute concerning Allah’s signs except those who disbelieve, so do not be deceived by their movement throughout the land.”
[Ghāfir: 4]

Further in the passage, He says:

“They disputed with falsehood to refute the truth thereby, so I seized them. How severe was My punishment!”
[Ghāfir: 5]

Allah Most High also says:

“We send the Messengers only as bearers of good tidings and warners. Yet those who disbelieve dispute with falsehood to refute the truth thereby.”
[Al-Kahf: 56]

His words:

“None dispute concerning Allah’s signs except those who disbelieve.”
[Ghāfir 4]

confirm the saying of the Prophet, may Allah bless him and grant him peace:

“Disputing about the Quran is disbelief.”

It is well known that anyone who opposes the Quran and argues against it on the basis of his own reason and opinions falls within the scope of this statement, even if he does not claim to give his own words precedence over the words of Allah and His Messenger. Indeed, if he says anything that gives rise to uncertainty and doubt concerning Allah’s words, he falls within its scope. What, then, of someone who claims that what he says on the basis of his own reason and opinions takes precedence over the texts of the Quran and Sunnah?